Roy Smith wrote:
"CFII_ASC" wrote:


Typically, to get it to go into the ACTV mode, these things must be
true:
1. In LEG mode (not OBS)
2. In ARM mode (this comes up when you have a valid approach loaded,
and you are within 30nm)


Within 30 nm of what? The IAF? The destination?

The FAF, I think, but someone else will give a more authoritative answer.



3. Valid RAIM now, and predicted at FAF and MAP
4. Outside FAF (110 degree arc each side of FAF)
5. Distance to FAF decreasing
6. Within 2nm of FAF, but not past (inside) FAF
7. NAV/GPS switch must be in the GPS position
8. No localizer frequency may be loaded into NAV 1 (some boxes)


Wow, that last one is pretty strange. I often have an ILS frequency
loaded up, even if I'm not using it. The most frequent use I make of
the NAV part of the GPS/NAV/COM is to fly an ILS, so the last ILS flown
is usually what's left there. What is the logic behind requiring me to
change it to something else?

The GX50 I had installed in my old Archer worked that way. I've also seen a GX50
that didn't work that way. It must be an installation option.

In the plane that wasn't installed that way, I've been safety pilot and seen a
confused pilot when he tuned the localizer without switching the GPS/NAV switch
to NAV, and couldn't figure out why the OBS wasn't behaving the way he thought
it should. OTOH, I can imagine the inverse kind of confusion occurring if the
OBS switched to NAV mode on its own when a localizer is tuned. You have to know
your installation.

What is the logic? Dunno.